Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A PROCESS FOR IRON ORE SINTERING FOR IMPROVING TOP LAYER SINTER PROPERTY USING CONSTANT COAL/COKE METHOD.



2 APPLICANT (S)

Name : JSW STEEL LIMITED;

Nationality : An Indian Company.

Address : Dolvi Works, Geetapuram, Dolvi, Taluka Pen, Dist. Raigad, Maharashtra-402107,India; Having the Registered Office at
JSW CENTRE,BANDRA KURLA COMPLEX,BANDRA(EAST), MUMBAI-400051, STATE OF MAHARASHTRA, INDIA.




3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
The present innovation relates to a process for iron ore sintering and a method of improving the sintering property. More particularly, the present innovation is related to improvement in top layer sinter properties like sinter yield and reduction in internal fine generation. The improvement in sinter yield and reduction in internal fine generation increases the throughput of the sinter plant to the blast furnace. The improvement is based on the concept of a constant total fuel ratio in the sinter feed mix, by increasing the total heat input in the sinter top layer. According to the present innovation, a method is provided in which a fraction of coke/coal is charged on the sinter top layer from the total coal/coke. The coal/coke is added before ignition. The combustion of coal/coke onto the sinter top layer during ignition provided the necessary heat required for the heating and melting of the sinter feed mix.

BACKGROUND OF THE INVENTION:
The existing system in sinter making utilizes raw materials like iron ore fines fluxes such as limestone, dolomite, and quick lime and fuel as coke/coal for the iron ore sintering process. Coke is the only source that provides heat during the sintering process. The sintering process is a heat-efficient convective heat transfer process. During the sintering process, heat generated after the combustion of coke gets transferred from the top part to the bottom part of the sinter bed due to negative suction. The heat pattern is varying from top to bottom due to the accumulation of heat in the sinter bed. The top part of the sinter bed is a “layer of heat deficiency” as this layer is in direct contact with the atmosphere compared to the middle and bottom layers.
Due to less heat availability in the top layer of the sinter bed, the rate of sintering reaction is less compared to the middle and bottom layers. Therefore, the top layer experiences weak sinter properties. Various research and patent have been published to improve the top layer sinter properties.
Patent application no. IN201931007717 dated 27-02-2019 disclosed the use of Wustite-enriched material mainly mill scale of suitable thickness on the sinter top layer and reported improvement in tumbler index and reduction in sinter fine generation. The use of a mill scale is nowadays not entertained much in the sintering process as the mill scale contains hydrocarbon residue of heavy grease which is not burned in the sintering process but is volatilized and gets entrapped in the filter bags of the electrostatic precipitator. This entrapped volatile material catches fire when waste gas and air are filtered.
Patent application no. JP 61223136 discloses the use of a screen constituted by a plurality of wire materials extending along the length of the segregation plate. During the charging of the sinter feed mix in the pallet car, segregation of the sinter feed mix takes place as per the size of the sinter feed mix. The finer material will be segregated in the top layer and coarse and intermediate layers in the middle and bottom layer of the pallet car. This prior art claims improvement in sinter yield and productivity owing to improvement in airflow across the sinter bed. This prior art has the complexity of the installation of a screen in the sintering machine and its maintenance as the screen may get clogged due to the moisture content of the sinter feed mix.
Japanese Patent application Laid-Open No. 58-133333 discloses a method of incorporation of electromagnet in the roll feeder. As soon as the sinter feed mix from the raw mix hopper falls on the roll feeder, electromagnet installed in the roll feeder exerts magnetic force on the metallic iron present in sinter feed mix and to its falling speed. Because of this magnetic force, small size particle is more affected compared to coarse particle. Thus coarse size particle falls earlier in pallet car compared to small size particle. It is claimed that the coarse particle settled at the bottom part of pallet car and fine particle on to the top part of pallet car. Thus, a state of segregation is obtained.
The claims made in the said patent is difficult to maintain on continuously in plant scale because as soon as the material falls from the roll feeder to the segregation plate, inverse segregation may happen and also to separate Fe from the sinter feed mix, repeatedly ON and OFF operation of electromagnet has to perform which will affect the magnetic force action. Hence, stable segregation is difficult to obtain.
Patent application number JP33998298A discloses a method of segregating fine coke in the upper layer of sinter feed mix in a pallet car. To obtain a sufficient degree of sintering and improve the yield of product in the sinter top layer, a magnetizing device is installed at the back surface side of a segregation plate which is installed between the drum feeder and pallet car, and a magnetizing device provided in parallel with the magnetizing device which applies static electricity to the flow of the cut sintering raw material to attract coke breeze in the sintering raw material to the lower side in the flow of the sintering material. The claim states that because of the segregation of coke in the sinter top layer, the degree of sintering in the sinter top layer has improved.
The claimed method in actual plant condition is difficult to maintain because of the complexity of the installation of the said apparatus and secondly, in a long run, the maintenance of such a device is difficult to maintain because of ample space available in the sinter machine.
To summarize, “all the above patents claim to solve sinter top layer properties but all of them reported overall change or improvement in sinter property”. Apart from this, the claimed methods are difficult to maintain in the long run of the sinter plant because of the complexity involved in the maintenance of the device installed in the segregation plate and drum feeder.
The present innovation solves the above-mentioned problems and obtains sufficient improvement in the degree of sintering in the sinter top layer (sinter yield and reduction in return fine generation) by increasing the total heat input in the sinter top layer. According to the present innovation, a method is provided in which a fraction of coke/coal is charged on the sinter top layer from the total coal/coke. The coal/coke is added before ignition. The combustion of coal/coke onto the sinter top layer during ignition provided the necessary heat required for the heating and melting of the sinter feed mix. This layer as stated earlier is a heat-deficient area resulting in poor sintering due to its direct interaction with the atmosphere post-ignition which causes a quenching effect.

OBJECTIVE OF THE INVENTION
The basic object of the present innovation is thus directed to a process for iron ore sinter production using sprinkling of coal/coke on the top layer of the sinter bed to improve the sintering property.
A further object of the present innovation is to provide a process for sinter production using coal/coke sprinkling on the top layer of the sinter bed which will increase the total available heat in the top layer of the sinter bed. This increase in total heat results in an increase in the temperature of the top layer of the sinter bed which increases the melting rate and improves the sintering property.
A further object of the present innovation is to provide a process for sinter production using coal/coke sprinkling on the top layer of the sinter bed which increases the total time spent by the flame front in the top layer of the sinter bed above 1100°C.
A further object of the present innovation is to provide a process for sinter production using a sprinkling of coal/coke on the top layer of the sinter bed, favouring an increase in the FeO% of the top layer of the sinter bed. This increase in FeO% is attributed to an increase in the total heat supplied to the sinter top layer via a sprinkling of coal/coke.
A further object of the present innovation is to provide a process for sinter production using coal/coke sprinkling on the top layer of the sinter bed which will increase the sinter yield in the top layer of the sinter bed without affecting the yield of the middle and bottom layer of sinter bed.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a process for iron ore sintering including advancement in top layer sintering yield and characteristics comprising:
i) computing sinter mix mass balance based on the sinter to be produced including required coal /coke constitution;
ii)preparing the sinter feed mix involving selectively 3.5to 6.6 %of the required said total coal/coke constitution of the thus computed sinter mix mass balance and feeding the said sinter feed mix on the sinter machine for sintering in layers of sinter bed ;
iii)charging by sprinkling the remainder of 2.1 to 8.4% of the said total coal/coke of the computed sinter mix mass balance on the top layer of the sinter bed;
iv)carrying out combustion of coal/coke on said top sinter layer during ignition for sintering for effective heat utilization of sintering process by increased heat input in the sinter top layer based on the thus sprinkled part of the coal/coke on the sinter top layer for desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5% to 18.8% of the total sintering period favouring primary slag formation and thereby increased FeO % in top layer in the range of 10.9 to 12.5 %

A further aspect of the present invention is directed to said process wherein said sinter feed mix comprising by wt%

Iron bearing raw materials: 75 to 88% including iron ore fines(-10mm) 1.3 to 4.32%,
fluxes 8.5 to 19.5%; and
fuel as coke/coal fines 3.5 to 6.6%, and
wherein said sprinkled coal/coke to the sinter top layer is combusted involving vertical/side burners, such that heat available on the sinter top layer enhances the melting in the sinter top layer and subsequently conveyed to the thereunder middle and bottom layers.

A still further aspect of the present invention is directed to said process comprising
i) computing sinter mix mass balance based on the sinter to be produced including required coal /coke constitution;
ii)preparing the sinter feed mix involving selectively 2.1 to 8.4% of the required said total coal/coke constitution of the thus computed sinter mix mass balance and feeding the said sinter feed mix on the sinter machine for sintering in layers of sinter bed;
ii)preparing the sinter feed mix involving selectively 3.5 to 6.6 % of the required said total coal/coke constitution of the thus computed sinter mix mass balance and feeding the said sinter feed mix on the sinter machine for sintering in layers of sinter bed ;
iv)charging by sprinkling in varying amounts from 2.1to 8.4%, preferably 4.2%, on the top layer of the sinter feed mix of the said total coal/coke of the computed sinter mix mass balance on the top layer of the sinter bed;
v)carrying out combustion of coal/coke on said top sinter layer during ignition for sintering for effective heat utilization of sintering process by increased heat input in the sinter top layer based on the thus sprinkled part of the coal/coke on the sinter top layer for desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5 to 18.8%of the total sintering period favouring primary slag formation and thereby increased FeO % in top layer in the range of 10.9 to 12.5 %.
A still further aspect of the present invention is directed to said process, which increases the sinter yield upto 8.6% from the top layer; upto 2.5% from middle layer; and 4.1 % for the sinter obtained from the bottom layer leading to an overall yield up to 4.8% by sprinkling of coal/coke (up to 6.6% of the total coal/coke) in top layer compared to the base case where no coal/coke is sprinkled on top layer of sinter bed.

A still further aspect of the present invention is directed to said process which provide the yield in the range of 81% to 88% preferably 88% a for sinter obtained of top layer; Yield in the range of 86.5% to 90.7% preferably 90.6% for the sinter obtained of middle layer; and Yield in the range of 91.3% to 95% preferably 95% for the sinter obtained of bottom layer.

Another aspect of the present invention is directed to said process for iron ore sintering wherein sintering process parameters comprising:
S.I No. Parameters Value
1 Bed height 0.4-0.75m
2 Hearth layer 0.02-0.06 m
3 Ignition time 60 -180 s
4 Suction during ignition 500-1500mm WC
5 Suction during sintering 1250-3000 mm WC
6 Moisture 5.5 -9.5 +/- 0.2 %

A still further aspect of the present invention is directed to a system for carrying out the process for iron ore sintering including advancement in top layer sintering yield and characteristics as described above comprising;

sinter machine including sinter bed for layered feeding of the sinter mix;

drum feeder and cooperative separation plate for desired controlled feeding of sinter mix on said sinter bed;

silo for feeding the coal/coke charge on top sinter mix layer; and

vertical/side burners facing said top sinter mix layer for carrying out combustion of the coal/coke charge on said top layer for desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5 to 18.8% of the total sintering period favouring primary slag formation and thereby increased FeO% in top layer in the range of 10.9 to 12.5 %.

The above and other aspects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying drawings and example.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1: Shows schematic view of actual sinter plant.
Figure 2: shows the Pot sintering test set-up.
Figure 3: shows Typical image of top layer of sinter bed post ignition.
Figure 4: shows comparison of sinter yield from top to bottom layer.
Figure 5: shows Percentage change in sinter yield- in layers and overall.
Figure 6: Shows process flow sheet-standard versus modified.
Figure 7: shows Comparison of lab scale (L) and sinter plant results where the graphical plot demonstrates the industrial and lab scale data trend.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO DRAWINGS
Sintering is a technology for the agglomeration of iron ore fines and fluxes and fuel (coal/coke) fines into useful Blast furnace burden material for hot metal production. The raw materials used for sintering are of different sizes such as iron bearing fines (+12 to 0.15 mm), fuel (coal/coke) breeze (-3 mm), fluxes (-3mm), and return sinter (-5 mm). The proportioned raw material is then mixed and moistened using normal process water in a mixer drum. The mix is then loaded on the sinter machine through a drum feeder on a moving grate to produce product sinter.
The present innovation relates to a new method wherein the addition of a fraction of coal/coke from the total calculated coal/coke is charged on the top layer of the sinter feed mix. The addition of a fraction of coal/coke during its combustion provides the necessary heat required for heating and melting the sinter feed mix.
In the new method, coal/coke is added in varying amounts from 2.1to 8.4% on the top layer of the sinter feed mix. The total coal/coke consumption, however, remains constant.
Therefore, such as herein described is a new method of sintering process for achieving higher productivity comprising the steps:providing sinter raw mix such as iron bearing fines, and fluxes and fuel (coal/coke) fines in weighed proportion and then the transfer of the sinter raw mix through conveyer in a first mixer drum first, where dry mixing of sinter feed mix takes place and then it is transferred to nodulizer where water for moistening the feed mix is added to obtain granulated sinter feed mix. Afterward, a measured amount of coal/coke is sprinkled onto the top layer of the sinter feed mix. An ignition hood consisting of a burner (vertical/side) is installed to initiate the combustion of the top layer of the sinter feed mix. Once, the ignition is completed, the combustion of the sinter feed mix propagates in the downward direction because of the negative suction.
Before the ignition of the sinter feed mix, weighed amount of coal/coke is sprinkled on the top layer of the sinter feed mix. When the sprinkled coal/coke comes in contact with the ignition flame, a sudden increase in total heat generated is observed. The increase in extra heat enhances the sintering reaction and improves the degree of sintering.
In the sintering process, it is well-established that there is an imbalance of heat distribution from the top to bottom layer of the sinter bed. The top layer of the sinter bed post-ignition experiences much faster cooling compared to the middle and bottom layers because of the absence of pre-heated flue gas in the top layer of the sinter bed. However, due to downward suction, when the hot flue gas from the top layer reaches the middle and then to the bottom layer, the heat present in the flue gas pre-heats the middle and bottom layer and is followed by coke combustion. Due to this the total heat availability in the middle bottom increases and enhances the sintering reaction compared to the top layer of the sinter bed.
Typically sinter plants conventionally use 3.5 to 6.6 % of coal/coke in sinter feed mix. In present experiment, 4.5-5.2% coal/coke is used in the total feed mix.
Out of this, applicant proposed to use 0-6.3% coal/coke on the top layer by sprinkling (this is the novelty) and remaining in the original feed mix as per the standard practice.
The disclosed method of sprinkling coal/coke on the top layer of the sinter bed in varying amounts thus solves the problem of heat deficiency. By sprinkling coal/coke in the top layer, it prolongs the time spent above 1100°C, an important sintering temperature where primary slag formation takes place. This increase in the sintering time enhances the sintering reaction and minimizes the loss of heat because of the sprinkling of a part of coal/coke from the total coal/coke. The disclosed method uses the principle of accumulation of heat in the sinter bed because of the downward or negative suction. Hence, the extra heat generated because of the sprinkling of coal/coke solves the heat deficiency in the top layer of the sinter bed, and secondly, because of the negative/downward suction, heat present in flue gas when it flows from top to bottom layer preheats the sinter mix. Thus this method enhances the efficiency of coal/coke utilization in sinter making and the overall sintering process.
Accompanying Figure 6 show process flow sheet-standard versus modified.
DESCRIPTION OF THE PROCEDURE OF EXPERIMENTS UNDER THE INVENTION (POT SINTERING TESTS):
A typical industrial scale sinter machine is shown schematically in Figure 1. The present invention discloses the sintering machine 8 in which sinter feed mix 1 with calculated fuel is charged in sinter bed 8. The sinter feed mix falls on the drum feeder 3 and through segregation plate 4, the sinter feed mix falls onto the pallet car. An ignition burner 6 with vertical/side burner 7 is provided to initiate the combustion of sinter top layer 9. The sinter feed mix contains a total of 3.5 to 6.6% coal/coke. To improve the property of the top layer of the sinter bed, 2.1, 4.2, 6.3, & 8.4 % out of the total coal/coke (100%) is added to the sinter top layer 5 from silo 2 in different sets of experiments. As soon as it comes in contact with vertical burners 7, the total heat available on the sinter top layer increases which decreases the quenching effect of the atmosphere after ignition. This enhances the melting in the sinter top layer 9 and subsequently in the middle 10 and bottom layer 11.
Figure 2 shows the schematic of the sinter pot on which lab-scale experiments have been carried out. All the sintering experiments were carried out with the sinter mix used in the actual sinter plant of Applicant’s JSW Steel Dolvi works, India.
Sinter feed mix after weight proportioning was first dry mixed and then granulated in a nodulizer. After feed mix preparation, the granulated sinter feed is charged in the sinter pot 3. A pre-determined amount of hearth material 4 is charged first in sinter pot 3. Afterward, the granulated material 7 is charged in the sinter pot 3. Once the loading of granulated material 7 is completed, coal/coke 2 in varying amounts (2.1to 8.4%) is charged in the top layer of the sinter bed. As soon as the loading of coal/coke is completed, ignition hood 1 containing burners (vertical/side) initiates the combustion of the top layer of the sinter bed for a period of 70 s. Post the completion of ignition, the ignition front moves downward due to the negative draught created by ID Fan 9. The direction of wind flow is visualized in wind box 8.
A sufficient number of pot sinter experiments were carried out with varying amounts of coal/coke in order to produce the reproducibility of the results. The pot sinter result shows that 4.2% coal/coke addition brings a significant change in the properties of the top layer of the sinter bed.
Various process data during the pot sintering test were collected for analysis to understand the technological benefits/changes in sinter properties due to the addition of coal/coke in the top layer of the sinter bed.
The following procedure was followed in the experimental trials of pot sintering tests:
a) Preparation of samples for Physico-chemical analysis:
All the raw material samples are subjected to both chemical and physical analysis tests. In the physical analysis test, the raw materials are screened to different size fractions and added as sinter feed mix shown in Table 1, and chemical analysis of the feed mix is done by using XRF shown in Table 2.

Table 1 Sinter feed mix distribution (mass%)
Sr.No. Raw material mass%
1 Iron bearing material 75-88
2 fluxes 8.5-19.5
3 Fuel (Coal/coke) 3.46 -6.56

Table 2 Chemical analysis of sinter feed mix (wt.%)
Raw materials Fe(T) SiO2 Al2O3 CaO MgO Moisture LOI

Iron bearing raw material 50.7-62.9 2.9-7.0 2.4-4.2 0.01-12.1 0.06-2.2 1.1-7.9 3.6-8.9
Flux 0.6-0.9 0.7-2.7 0.2-0.8 32.8-90. 0.5-19.5 0.2-0.7 5.9-45.5
Fuel (Coal/coke) 0.5-0.6 6.6-7.7 3.9-4.4 0.5-0.7 0.1-0.2 6.9-7.3 83.1-84.1

b) Charge calculations for pot sinter experiments:
Charge calculations for pot sinter experiments were done on the basis of four equations:
• LOI balance
• Total Fe
• MgO balance
• CaO balance
Once the required compositions percentage of different raw materials is found using the above mass balance equations, the raw material is weighed using an electronic balance. Pot sinter experiment plans were designed with three repeat trials.
Pot sinter test conditions were shown in Table 3
d) Preparation of raw materials for sintering:
All the weighed material after mass balance is first dry mixed in a mixer drum for five minutes in the primary mixing drum and then it is transferred to the secondary mixing drum/nodulizer. Water for wet mixing/nodulization of raw sinter feed mix is estimated based on the moisture level requirements of the sintering process, which also depends on the sinter feed mix water absorbing capacity.After confirmation of the required moisture in the sinter feed mix, the sinter feed mix (approximately 75 kg) is then fed into the sinter pot manually in the tray after weighing in the digital weighing machine.
e) Sintering process with granulated sinter feed mix:
The sinter pot is geometrically cylindrical in shape with 600 mm in height and 300 mm in internal diameter. The bed height chosen here is as per the actual bed height maintained at the respective sinter plant. It is done so as to simulate the actual sinter plant conditions so that the test results can be correlated.
The sinter pot with granulated sinter feed mix is mounted on the top of the wind box and the gap between the sinter pot and wind box is sealed by nuts and bolts. Before the start of the sintering process, a weighed amount of coal/coke (2.1 to 8.4%) is sprinkled on the top layer of the sinter feed mix in a different set of experiments. After the sprinkling of coal/coke on the top layer of the sinter feed mix, the air blower of capacity 2700 mm WC is switched on to create the necessary suction beneath the grate bar. A suction of around 500 mm WC is maintained during ignition (one minute) and then the suction is increased gradually to 1250 mm WC for the rest of the sintering process. During the sintering process, the suction and temperature of the wind box are continuously monitored. When the wind box temperature reaches a peak, it starts to decline, considering the sintering temperature. This peak wind box temperature is defined as the breakthrough point (BTP) marked as the end of the sintering process.
After sintering is completed, it is kept for overnight cooling since it is very hot to handle manually. The sinter pot is then stripped to get the sinter cake with the help of a hoist crane.
The sinter cake is then divided into three equal parts and is nominated as the top, middle, and bottom layers(Figure 1). Each layer is then subjected to a shattering test from a height of 2 m to simulate the star crusher activity in the actual sinter plant. The sinter cake in the shatter test is allowed to fall on a metal base plate of thickness 0.02 m. This test is carried out two times to balance the return sinter fine. After this, the sinter samples are subjected to the physical screening process. In the process, the sinter is screened as +40 mm, +20 mm, +10 mm, +8 mm, and +5 mm fractions to estimate their percentage in the total material. The +5 mm size fractions of the sinter are considered the final product of the sintering process. Sinter yield is calculated as the fraction of +5 mm size sinter to the total sinter weight.
Table 3 Pot sinter test conditions used for pot sinter experiments
S.I No. Parameters Value
1 Bed height 0.4-0.75m
2 Hearth layer 0.02-0.06 m
3 Ignition time 60 -180 s
4 Suction during ignition 500-1500mm WC
5 Suction during sintering 1250-3000 mm WC
6 Moisture 5.5 -9.5 +/- 0.2 %

The following parameters were measured during the experiments:
• Sintering time (Total time)
• BTP temperature
• Suction pressure
The following parameters were calculated through the experiments:
• Sinter yield (Y)
• FeO%
The following pot sinter results were obtained using coal/coke sprinkling on the top layer of the sinter bed:
Table 4 Pot sinter test results
Top Layer Middle Layer Bottom Layer
Exp. No. coal/Coke sprinkled in the top layer from total coal/coke (%) Y Y Y
1 0.0 81.2 88.4 91.3
2 2.1 86.2 90.7 94.5
3 4.2 88.0 90.6 95.0
4 6.3 81.0 89.4 94.0
5 8.4 81.5 86.5 94.1

Accompanying Figure 4 shows comparison of sinter yield from top to bottom layer and
Figure 5show Percentage change in sinter yield- in layers and overall.
It is observed that sintering properties like sinter yield increases with an increase in the sprinkling of coal/coke on the top layer of the sinter bed. The improvement in sinter yield will reduce the generation of internal fine which intern increases the sinter plant productivity. The test result shows that the sinter yield is 81.2% (internal fine generation is 18.8%) with 0 % coal/coke sprinkling on the top layer of the sinter bed. The sinter yield increased by 8.4% which reduces the internal fine generation by 36.2% with 4.2% coal/coke sprinkling on the top layer of the sinter bed. However, with a further increase in coal/coke sprinkling on the top layer of the sinter bed, a decrease in the sinter yield of the top layer is observed. Table 5 shows the chemical analysis of the top layer of the sinter bed. FeO is an indication of the thermal content of the sinter bed. Sinter chemistry shows that FeO increases with an increase in coal/coke sprinkling on the top layer of the sinter bed and becomes maximum with 4.2% coal/coke addition. Similar to sinter yield, FeO% also decreases with further addition of coal/coke. The improvement in sinter properties of top layer is discussed in further section.
Table 5Chemical analysis of pot sinter test results
Exp. No. Coal/coke (%) T.Fe FeO CaO MgO SiO2 Al2O3
1 0.0 52.4 11.2 13.5 1.9 5.9 3.1
2 2.1 53.7 11.4 12.9 1.8 5.5 3.1
3 4.2 53.1 12.5 13.2 1.8 5.4 3.1
4 6.3 53.4 11.3 13.5 1.9 5.3 3.2
5 8.4 52.8 10.9 13.4 1.9 5.8 3.1

Physical analysis of the top layer of the sinter bed (Figure 3) shows the maximum temperature attained in the top layer of the sinter bed and time spend in the top layer post-ignition. With the addition of coal/coke on the top layer of the sinter bed, the assimilation/melting of the sinter feed mix has improved. With 0% of coal/coke, un-sintered material (brownish)is observed. With the increase in coal/coke, the un-sintered material in the top layer decreases and maximum temperature attained in the sinter top layer increases. Maximum improvement in top layer of sintering is observed with 4.2% coal/coke addition. However, with 6.3 and 8.4% coal/coke addition, sinter yield and maximum temperature decreased. This is attributed to the ash generated post ignition of coal/coke on top layer of sinter bed. It is well established that coal ash restricts the movement of gas and hence affects the heat distribution. Sintering process is a convective heat transfer process. Physical evidence shown in figure 3 shows that because of restriction of gas movement in top layer of sinter bed, a massive portion of heat is lost to the environment and the benefit of heat transfer post ignition of coal is not gained with 6.3 and 8.4% of coal/coke. This theory has been validated by the time temperature plot shown in table 6.

The summary of the time-temperature plot is tabulated in table 6. With the sprinkling of coal/coke on the top layer of the sinter bed, the maximum temperature attained in the top layer of the sinter bed increases. It is established that maximum temperature and time above 1100°Cis an important parameter that defines the degree of sintering. This increase in temperature is required for the melting of the sinter feed mix. Thus higher the sintering temperature, the higher will be the degree of sintering and the higher will be the sintering property. Table 6 shows that the maximum temperature in the top layer of the sinter bed is 4.2%of coal/coke sprinkling. The maximum temperature attained here is 101°C more than the base case and time spent above 1100°C is also 172 s compared to the base case of 69 s. However, with a further increase in coal/coke sprinkling in the top layer of the sinter bed, the maximum temperature reached in the sinter bed is decreased followed by a decrease in time spent above 1100°C. This explains that the heat loss to the ambient atmosphere is high due to the gas flow restrictions caused by coal/coke ash. Due to this gas flow restriction, gas flows in a particular area or through the channel. Thus affecting the proper heat distribution and hence the sinter properties.
Table 6 Summary of the time-temperature plot
Total Coal/Coke (%) coal/Coke sprinkled in the top layer from total coal/coke (%) T max (°C) Time to reach 1100°C (s) Time spent above 1100°C (s)
100 0 1230 442 69
97.9 2.1 1256 474 124
95.8 4.2 1331 387 172
93.7 6.3 1294 328 146
91.6 8.4 1255 328 114

Reported results are based on the pilot scale pot sinter study, which is a well-established practice in the field of iron ore sintering. Generally, users (i.e. sinter plants) prefer to conduct experiments using laboratory scale pot sinter machine and extrapolate the findings to the industrial scale, which are known to show reasonable correlation.
Accompanying Figure 7 show Comparison of lab scale (L) and sinter plant results where the graphical plot demonstrates the plant and lab scale data trend.
In the present invention, above reported lab scale pot sinter results show that by sprinkling 0 to 8.4%, preferably 4.2%, of total coal/coke in top layer and balance in the total feed mix leads to an improvement in the yield of top layer by 8.4% and overall yield by 4.8% which is expected to be in the similar range in the industrial scale.

, Claims:We Claim:
1. A process for iron ore sintering including advancement in top layer sintering yield and characteristics comprising :
i) computing sinter mix mass balance based on the sinter to be produced including required coal /coke constitution;
ii)preparing the sinter feed mix involving selectively 3.5 to 6.6 % of the required said total coal/coke constitution of the thus computed sinter mix mass balance and feeding the said sinter feed mix on the sinter machine for sintering in layers of sinter bed ;
iii)charging by sprinkling the remainder of 2.1 to 8.4 % of the said total coal/coke of the computed sinter mix mass balance on the top layer of the sinter bed using suitable device;
iv)carrying out combustion of coal/coke on said top sinter layer during ignition for sintering for effective heat utilization of sintering process by increased heat input in the sinter top layer based on the thus sprinkled part of the coal/coke on the sinter top layer for desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5 to 18.8% of the total sintering period favouring primary slag formation and thereby increased FeO % in top layer in the range of 10.9 to 12.5 %
2. The process as claimed in claim 1 wherein said sinter feed mix comprising by wt%

Iron bearing materials: 75 to 88% including iron ore fines(-10mm)1.3 to 4.32%,
fluxes 8.5 to 19.5%;
fuel as coke/coal fines 3.5 to 6.6wherein said sprinkled coal/coke to the sinter top layer is combusted involving vertical/side burners, such that heat available on the sinter top layer enhances the melting in the sinter top layer and subsequently conveyed to the thereunder middle and bottom layers.

3.The process as claimed in claim 1 comprising
i) computing sinter mix mass balance based on the sinter to be produced including required coal /coke constitution;
ii)preparing the sinter feed mix involving selectively 3.5 to 6.6 % of the required said total coal/coke constitution of the thus computed sinter mix mass balance and feeding the said sinter feed mix on the sinter machine for sintering in layers of sinter bed ;
iii)charging by sprinkling in varying amounts from 2.1 to 8.4% preferably 4.2%, on the top layer of the sinter feed mix of the said total coal/coke of the computed sinter mix mass balance on the top layer of the sinter bed;
iv)carrying out combustion of coal/coke on said top sinter layer during ignition for sintering for effective heat utilization of sintering process by increased heat input in the sinter top layer based on the thus sprinkled part of the coal/coke on the sinter top layer for desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5 to 18.8%of the total sintering period favouring primary slag formation and thereby increased FeO % in top layer in the range of 10.9 to 12.5 %.
4.The process as claimed in claim 3, which increases the sinter yield upto 8.6% from the top layer; up to 2.5% from middle layer; and 4.1 % for the sinter obtained from the bottom layer leading to an overall yield up to 4.8% by sprinkling of coal/coke (up to 6.6% of the total coal/coke) in top layer compared to the base case where no coal/coke is sprinkled on top layer of sinter bed.
5. The process as claimed in claim 3 which provide the yield in the range of 81% to 88% preferably 88% for sinter obtained of top layer; Yield in the range of 86.5% to 90.7% preferably 90.6% for the sinter obtained of middle layer; and Yield in the range of 91.3% to 95% preferably 95% a for the sinter obtained of bottom layer.
6. The process for iron sintering as claimed in anyone of claims 1 to 5 wherein sintering process parameters comprising:
S.I No. Parameters Value
1 Bed height 0.4-0.75m
2 Hearth layer 0.02-0.06 m
3 Ignition time 60 -180 s
4 Suction during ignition 500-1500mm WC
5 Suction during sintering 1250-3000 mm WC
6 Moisture 5.5 -9.5 +/- 0.2 %

7. A system for carrying out the process for iron ore sintering including advancement in top layer sintering yield and characteristics as claimed in anyone of claims 1 to 6 comprising;

sinter machine including sinter bed for layered feeding of the sinter mix;

drum feeder and cooperative separation plate for desired controlled feeding of sinter mix on said sinter bed;

silo for feeding the coal/coke charge on top sinter mix layer; and

vertical burners facing said top sinter mix layer for carrying out combustion of the coal/coke charge on the said top layer for the desired flame front in the top layer of the sinter bed above 11000C for a period of 12.5 to 18.8%of the total sintering period favouring primary slag formation and thereby increased FeO % in top layer in the range of 10.9 to 12.5 %.

Dated this the 24th day of December, 2022
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199